President of the South Australian Bar Association (SABA), Malcolm Blue QC, called for clarification of the legislative changes proposed under the Rann Government's recently released Serious Crime Policy 2010.

"It is very important that the intent of this proposal be clarified and understood ... so that the electorate is fully informed about the effect of the proposed legislation," he said in a statement released Monday.

Under the policy, prosecutors would be able to present to a jury evidence of an accused's past offences when "relevant" and "in the interests of justice".

However, a lack of preliminary detail within the policy means it is unclear whether this would result in any substantive deviation from the current law, and until further details are outlined, it is difficult to ascertain potential consequences.

Blue is concerned, however, that Australia's justice system could be undermined, especially if juries were presented with information regarding an accused's past offences for the purposes of determining guilt relating to a new offence.

"Such a proposal ... would have far-reaching consequences in changing the fundamental basis of our system of justice, namely the presumption of innocence and the principles that evidence upon which a conviction rests must actually and sufficiently prove the guilt of the accused," he said.

"The existing common law proceeds on the basis that it is prejudicial ... to conclude that someone is guilty of an alleged offence merely because they committed such an offence before."

The Law Society of South Australia (LSSA) has also voiced concern and has called for the establishment of a law reform body to facilitate public debate and access to information regarding the implications of such changes.

Law Society president Richard Mellows told Lawyers Weekly the LSSA has particular concerns about the integrity of the trial process.

"At the moment, the threshold for [presenting information about prior offences] is very high, for obvious reasons. A jury should be deciding a criminal case on the evidence before it, not on someone's [past behaviour]," he said.

According to Mellows, if the threshold was lowered, the integrity of the trial process would be jeopardised, thus leading to mistrials, re-trials and wrongful convictions. And, as such, a public body in which public debate and information is available is needed.

"We are talking about having a law reform body which is in the public domain, to which the public has access, and to which they can make submissions [so] that everyone understands the impacts, not just the Government ... not just a select few," Mellows said.